Some years ago, portable remote gas detectors have been developed for checking the presence of a gas leak from a distance by hand-scanning a laser beam across a target region. Such target region would typically be the neighborhood of a gas pipe or a gas pipe network. Portable remote methane detectors are e.g. available under the trademark LaserMethane. These devices emit a laser beam and receive a fraction of backscatter from the target region to measure the concentration-length product of methane between the detector and the target. As explained in the paper “LaserMethane™—A portable remote methane detector”, by Takaya Iseki, the technique used is tunable diode laser absorption spectroscopy (TDLAS), more specifically second-harmonic detection of wavelength modulation spectroscopy (WMS). The interested reader may refer to that paper and the references cited therein to learn the details of that technique. The known person-portable gas detection device is equipped with a visible red laser pointer to show the point currently aimed at. When the presence of gas is detected in the checked direction, i.e. if the concentration-length product exceeds a predetermined threshold, the remote gas detection device issues an alarm signal to warn its user.
A disadvantage of the known remote gas detection device is that there is some risk for the operator to miss a leak because of an imperfect manual scan of the target area. Indeed, even a concentrated user could accidentally forget to point at some zones of As a consequence, the reliability of a leak detection campaign using the handheld gas detection device depends to a large extent on the completeness of the manual scan.
Another drawback of the known handheld gas detection device is that the manual scanning of large areas may take a long time.